1. Technical Field
The present invention concerns an apparatus for matching an analog switching system with a digital switching system to exchange signals between them.
2. Related Art
Generally, the analog switching system is a manual switching system installed in a rural network area which is not provided with means for utilizing the main network installed in an urban area. The analog switching system employs the long distance subscriber line signal handled by the rural network, and provides the long distance subscribers with calling service by making a connection with a central exchange which is installed in the urban area typically located over a few hundred kilometers from the analog switching system.
Typically, such analog switching systems require an analog-to-digital (A/D) converter, such as a PCM30-4 (A/D converter) in order to achieve a system which is harmonious with a digital switching system. However, since such systems are typically designed according to the signaling system known as R1, R2/CAS, such a system may not be employed in a rural network system as generally described above, and as described in more detail below. Therefore, there has been a requirement for a signal conversion system to process a 2-wire long-distance subscriber line signal so as to match the digital switching system with the analog switching system typically employed in a rural network system.
Thus, there is a need in the art to provide a signal matching system which matches a digital switching system with an analog switching system using a 2-wire long-distance subscriber line signal.
The following patents are considered to be representative of the prior art, and are burdened by the disadvantages set forth herein: U.S. Pat. No. 4,535,444 to Falzone et al, entitled Digital Switching Exchange For Telephone Systems, U.S. Pat. No. 5,657,358 to Panech et al, entitled Subscriber RF Telephone System For Providing Multiple Speech And/Or Data Signals Simultaneously Over Either A Single Or Plurality OfRF Channels, U.S. Pat. No. 5,687,194 to Paneth et al., entitled Subscriber RF Telephone System For Providing Multiple Speech And/Or Data Signals Simultaneously Over Either A Single Or A Plurality Of RF Channels, U.S. Pat. No. 5,325,422 to Ladd, entitled PBX Telephone Call Control System, U.S. Pat. No. 4,796,296 to Amada et al, entitled PCM Coder And Decoder Having Function Of Two-Wire/Four-Wire Conversion, U.S. Pat. No. 4,757,497 to Bejerle et al., entitled Local Area Voice/Data Communications And Switching System, and U.S. Pat. No. 4,309,766 to Lechner et al., entitled ArrangementFor Subscriber Circuits UtilizingDigital Time Division Multiplex Telecommunication Installations And Particularly For PCM Local